1. Field of the Invention
The present invention relates to a rodless cylinder, and more specifically to a rodless cylinder wherein a load applied to a sliding table which is disposed outside a cylinder and displaced in accordance with the reciprocating motion of a piston, can be dispersed and supported on the cylinder side, thereby making it possible to smoothly move the sliding table in accordance with the reciprocating motion of the piston and to facilitate a further reduction in a space occupied by the rodless cylinder.
2. Description of the Related Art
In recent years, rodless cylinders have been widely used as workpiece feeding devices in factories or the like.
A rodless cylinder normally comprises a cylinder body having a slit defined therein so as to extend along the longitudinal direction thereof, and a sliding table. A piston put into the cylinder body is provided integrally with the sliding table by a connecting member.
The rodless cylinder can have a reduced in stroke as compared with a cylinder with a rod coupled thereto. Thus, the area occupied by the rodless cylinder is small and the rodless cylinder is easy to handle. The rodless cylinder can also prevent dust from entering therein as compared with the rod-coupled cylinder referred to above. As a result, highly accurate positioning operation can be effected.
This type of rodless cylinder has been disclosed in U.S. Pat. No. 4,373,427 or DE-PS 3,124,915, for example. In particular, the rodless cylinder described in DE-PS 3,124,915 is constructed such that a guide groove is defined in a given portion located outside a cylinder tube and a guiding means mounted to each of legs each of which extends toward the given portion from the ends of the sliding table, is fitted in each guide groove. According to DE-PS 3,124,915, when a lateral force is applied, the guiding means is held against the guide groove so as to avoid an increase in width of a slit.
According to DE-PS 3,124,915, however, each leg should be disposed so as to extend toward a position far spaced from the outer side of the cylinder tube as seen from the sliding table and to hold the guiding means. Thus, when the guiding means is fitted in the guide groove upon application of the lateral force, one end face of the cylinder tube, which defines the slit, forcibly approaches the other end face of the cylinder tube, which defines a slit on the opposite side. As a result, the inside diameter of a bore defined in the cylinder tube is reduced as a whole, so that a piston is forcibly inactivated. That is, the piston stops moving when the lateral force is applied. In other words, a workpiece feeding operation is unexpectedly stopped, thereby causing a problem that a workpiece held in engagement with the sliding table cannot be smoothly fed.